1. Field of the Invention
The present invention relates to a blower fan used, for example, to cool an electronic device, and a method of manufacturing such a blower fan.
2. Description of the Related Art
Outer-rotor motors, in which a rotor is arranged radially outward of a stator, have been predominantly used as motors for driving blower fans because they typically provide an easier assembling procedure, a reduced number of parts, and so on. In addition, in terms of performance, the outer-rotor motors typically have a greater moment of inertia and are able to achieve increased driving torque, and therefore are more easily able to maintain a constant rotational speed.
Meanwhile, as electronic devices have become increasingly dense in recent years the amount of heat generated by these increasingly dense electronic devices has also increased. As a result, there has been a demand for blower fans used to cool such electronic devices to rotate at a greater speed. The outer-rotor motors, however, may cause a problem in terms of strength, because an increased rotational speed of the blower fan leads to an increased vibration resulting from the great moment of inertia of the outer-rotor motors.
Blower fans using inner-rotor motors, in which the rotor is arranged inside of the stator, allow greater rotational speeds because the inner-rotor motors have a smaller moment of inertia than the outer-rotor motors.
U.S. 2009/0180901, for example, describes a blower fan using an inner-rotor motor. This blower fan includes a motor support portion in which a support portion (i.e., a bushing 233) arranged to support a bearing and a support portion (i.e., a position structure 232) arranged to support a stator are integral with each other.
The technique described in U.S. 2009/0180901, however, has problems because its motor support portion is made of a solid one-piece member defined by only a plastic or a metal.
That is, in the case where the motor support portion is made of a plastic or a metal, the support portion arranged to support the bearing is also made of the plastic or the metal, and it is therefore difficult to secure a sufficient vibration-resistant strength for an increased rotational speed of the blower fan.
Also, in the case where the support portion arranged to support the stator is made of a plastic or a metal, vibration that is generated in the stator may be transmitted to a housing through the plastic or the metal when the blower fan is caused to rotate at a great speed. Moreover, if the blower fan is caused to rotate at a great speed for a long time, the stator may generate too much heat to allow a sufficient heat radiation effect. It is therefore difficult to maintain reliability of the blower fan for a long time when the blower fan is caused to rotate at a great speed.